The invention involves a device for testing thin elements, such as wafers or individual substrates, while at the same time offering a facility for inspecting the reverse side of the thin elements.
FIG. 1 shows a normal device using state-of-the-art technology with a base plate 2 (ideally made from steel) which can be moved in an x/y direction, and with a central opening in which a substrate support 4 is inserted in the form of a thin glass plate. A substrate 5, e.g. a wafer, wafer parts or even individual substrates, is deposited on the substrate support and taken in/fixed to the edge on the outside of the glass plate via vacuum channels 18 located in the base plate.
In the middle under the opening is an inspection device, preferably an adjustable emission microscope 11 or similar.
Above the base plate 2 is a device 6 for making contact with the DUT (device under test), e.g. a probe card, probe head (probe manipulator, print module which is mounted in a probe holding plate 9 via a probe card adapter 7. The probe holding plate 9 can execute a manual or motor-driven vertical movement—via a separation device 16—for bringing the probes of the probe card 6 into contact with the substrate and for lifting the probe card 6 from the substrate 5 during x/y positioning of the base plate 2. Optionally, probe heads can also be used in place of the probe card. The heads are positioned on the probe holding plate 9 (SHP) and can be used to create special ambient conditions for the DUT.
The U.S. Pat. No. 5,493,236 C also shows a sampler on which the substrate to be tested (wafer), depending on its circumference, sits on a wafer support so that the remaining area of the reverse side of the wafer is free for an inspection device. The substrate is contacted by the needles of a probe card from the upper surface. This sampler is only suitable for inspecting small substrates, or comparatively low needle forces may be applied so that the substrate is not deflected.
A high deflection of the substrate support and/or of the substrate as a consequence of high contact forces exercised by the probe card would be particularly disadvantageous. Furthermore, such a device is entirely unsuitable for substrate diameters of 200 mm and above.
Finally, with the devices described, the edge of the substrate is required for secure fixing on the base plate, and therefore cannot be included in the inspection.